Pulsating universe

Pulsating Theory:

    Some astronomers believe that if the total mass of the universe is more than a certain value, the expansion of the galaxies would be stopped by the gravitational pull. Then the universe may again contract. After it has contracted to a certain critical size, an explosion again occours. The expansion and contraction repeat after every eight billion years. Thus we may have alternate expansion and contraction giving rise to a pulsating universe.